Spatial variations of the sodium/potassium ratio in Mercury’s exosphere uncovered by high-resolution spectroscopy ☆

High resolution spectroscopy of Mercury has been obtained with two different instruments in 2006: the EMMI instrument at the 3.6-m NTT telescope of ESO La Silla Chile and the Espadon spectrograph at the 3.6-m CFHT telescope on top of Mauna Kea (Hawaii). The disk of the planet has been scanned for spatial variation of the exospheric species. The large spectral range and high resolution allow simultaneous measurements of the integrated column density of Na and K